1. Field of the Invention
The present invention relates to an audio signal reproduction apparatus and method for reproducing at a speed different from the running speed of the recording medium when a data has been recorded.
2. Description of the Prior Art
In a video tape recorder using a magnetic tape for recording and reproducing a television signal, a digital video tape recorder (hereinafter, referred to as digital VTR) is used in practice as an apparatus for recording and reproducing a television signal without substantial deterioration.
This digital VTR records on a magnetic tape a television signal including a video signal, audio signal, control signal, and the like, as a digital data, and reproduced the digital data recorded on the magnetic tape.
The digital VTR records the digital data on an inclined recording track on the magnetic tape. This inclined recording track is formed by a rotary magnetic head (hereinafter, referred to simply as head) arranged with inclination in the longitudinal direction of the magnetic tape. A television signal of one frame after subjected to A/D conversion to obtain the aforementioned digital data is recorded on 10 adjacent tracks of the inclined recording track.
Among the digital VTR, there is an apparatus type allowing the user to select between a normal reproduction mode and a changed (slowed down) reproduction mode. In the normal reproduction mode, the tape travels at the same speed when recording has been performed. In the changed (slowed down) reproduction mode, the tape travels at a slower speed than the speed during recording.
For example, the digital data recorded on the magnetic tape by the digital VTR can be reproduced at a reduced speed by the JOG reproduction mode. However, this requires a pitch processing mainly related to the frequency of an acoustic stimulus.
Conventionally, in the jog reproduction mode, a pitch variable mode or a pitch fixed mode has been selected. That is, there has been no switching between the variable or fixed pitch mode in the jog reproduction.
On the other hand, if the pitch can be varied in the jog reproduction mode, as the reproduction speed is reduced the pitch is more lowered, and it becomes difficult to understand a conversation and it becomes impossible to isolate a word. When reproducing a music source, melody cannot be recognized. Moreover, in the reproduction processing, a valid number of data items decides the sound quality. If variable pitch lowers the speed and as the number of concealed data items increases, frequency of a noise component is lowered, the noise becomes offensive to the ear.
Moreover, if the pitch is fixed in the jog reproduction mode, when the reproduction speed is at super low, sound like xe2x80x9cgaw gawxe2x80x9d is generated which cannot be isolated from the noise.
The conventional pitch processing has the aforementioned problems.
It is therefore an object of the present invention to provide an audio signal reproduction apparatus and method capable of properly switching between a pitch fixed area and a pitch variable area in the jog reproduction mode, so that contents of a conversation and a melody of a music source can be recognized, as well as enabling to distinguish them from a noise and improve the sound clearness.
The audio signal reproduction apparatus for reproducing a digital audio signal based on a predetermined number of samples which have been recorded on a recording medium, said apparatus comprising: a reproduction means for reproducing from the recording medium the digital audio signal based on the predetermined number of samples; a pitch control means for performing pitch control of the digital audio signal reproduced; a speed detection means for detecting a reproduction speed of the recording medium from elements of a travel mechanism of the recording means; and a pitch decision means responding to the output of the speed detection means, and in a case if the reproduction speed of the recording medium is lower than the travel speed of the recording, so that the pitch control means decides a pitch variable period and a pitch fixed interval.
Moreover, in the audio signal reproduction apparatus according to the present invention, it is preferable that the pitch control means include: a sample count identification means for identifying the sample count of the digital audio signal based on the predetermined number of samples; a total sample count calculation means for counting the total number of samples used for the pitch control, using the sample count data identified by the sample count identification means and a reproduction speed information of the recording medium; and interpolation calculation means for generating an interpolation data for said pitch control according to the data indicating the total sample count calculated by the total sample count calculation means, wherein the pitch decision means has a speed information calculation means for converting the speed information from the speed detection means, into a speed information indicating a pitch variable period and a pitch fixed period, and supplying this modified speed information as a travel speed information of the recording medium, to the total sample count calculation means.
Moreover, in the audio signal reproduction apparatus according to the present invention, it is also preferable that the pitch decision means further include a pitch variable/pitch fixed specification means for forming a speed data for specifying the pitch variable period or the pitch fixed period, wherein according to the speed data, the speed information calculation means modifies the speed information corresponding to the pitch fixed period, to a value identical to a normal reproduction speed of the recording medium.
Moreover, in the audio signal reproduction apparatus according to the present invention, it is also preferable that the pitch variable/pitch fixed specification means outputs a speed data to specify the pitch fixed period when the reproduction speed of the recording medium is ⅓ to ⅕ speed mode.
According to another aspect of the present invention, there is provided an audio signal pitch control method when reproducing a digital audio signal based on a predetermined number of samples, at a speed different from the speed of the recording medium travel during recording, the method comprising: a reproduction step for reproducing from the recording medium the digital audio signal based on the predetermined number of samples; a pitch control step for performing pitch control of the digital audio signal reproduced in the reproduction step; a speed detection step for detecting a reproduction speed of the recording medium from elements of a travel mechanism of the recording means; and a pitch decision step for deciding the pitch in response to the output of the speed detection step, so that if the reproduction speed of the recording medium is lower than the travel speed of the recording, the pitch control step decides a pitch variable period and a pitch fixed interval.